Mercury

How Does Electronic
Waste Contribute Mercury to the Environment?

Electronic
waste (e-waste) contributes many harmful substances to the environment. Mercury
is one of these. Mercury can enter the environment through the improper
disposal of fluorescent tubes, tilt switches (switches in thermostats and other
mechanical devices), older computers, batteries and even paint (epa.gov). Once
in the environment, mercury can have very harmful effects, especially because
it does not filter quickly.

Ecological Impacts of
Mercury

Mercury
is a known toxic compound which has significantly increased its prevalence in
natural ecosystems over the last 30 years (Mercury report to Congress, 1997).

Mercury can exist in the environment
as either a gas, liquid or as solid particles. This enables mercury to enter
ecosystems through multiple avenues. Mercury is most dangerous, however, when
it reacts with other chemicals to form methylmercury, an organic compound. Data
gathered by Watras et al. showed that “methyl-Hg is more efficiently
transferred up aquatic food chains and less efficiently excreted that inorganic
Hg” (Watras et al., 1992). This aspect of mercury means that it is able to
“bioconcentrate, bioaccumulate and biomagnify. In fact, mercury is one of the
few metals that is known to biomagnify in aquatic food webs” (Mercury report to
congress, 1997). In addition, loading of
mercury will not present itself as methyl mercury within an environment
immediately (Paterson et al., 2006). Thus, the currently levels of methyl mercury
measures are not reflective of the current levels of mercury loading, which are
much higher now than they have been in the past. The implications of this are
great and far reaching.

(Mercury
Reports to Congress, 1997).

Bioaccumulation and Biomagnification

Bioaccumulation refers to the uptake
of a chemical in living organisms over time. Conversely, biomagnification is
“the increase in chemical concentration in organisms at successively higher
tropic levels in a food chain as a result of the ingestion of contaminated
organisms at lowers trophic levels” (Mercury Reports to Congress, 1997).
Initially, higher levels of mercury in larger organisms was thought to be a
product of longer lifespan, however, studies have increasingly shown that
higher concentrations are a result of biomagnification (Watras, 1992; Morel et
al. 1998; Sampiano et al, 2005). This effect is compounded by mercury’s long
retention time in soils; mercury can “continue to be released to surface waters
for long periods of time, possibly hundreds of years” (Mercury report to
congress; Johansson et al. 1991).

Sources of Exposure and Contamination

Organisms can be exposed to mercury
through contact with exposed substances, such as earthworms in soil or fish in
water, or through ingestion of already contaminated organisms or materials,
such as grazers eating plants from contaminated soil (Mercury report to
congress).

(Mercury Report To Congress, 1997)

(Mercury
Report To Congress, 1997)

Ecological Impacts

Mercury uptake by plants is
extremely harmful. They show damage to structure and phytomass, decreased
amounts of chlorophyll, as well as plant death in some species (Mhatre, 1985;
Sarkar and Jana, 1986).

At
risk ecosystems for mercury absorption need to be particularly avoided when
dealing with electronic waste. These ecosystems include areas with high
concentrations of avian and aquatic organisms, as these are primary targets for
mercury bioaccumulation. These areas particularly at risk due to the high
levels of organismal exposure to the environmental system, and thus are more
susceptible to the effects, even indirectly.

(Mercury Report To Congress, 1997)

Other sources for more information on the effects of Mercury in ecosystems:

United States. Environmental Protection Agency. Office of Air Quality Planning and Standards. & United States. Environmental Protection Agency. Office of Research and Development. 1997 Mercury study report to Congress. Office of Air Quality Planning and Standards and Office of Research and Development, U.S. Environmental Protection Agency, [Research Triangle Park, N.C.] : http://purl.access.gpo.gov/GPO/LPS1629